Assessment of the neurologic effects of dietary deficiencies of phenylalanine and tyrosine in cats

Objective—To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats. Animals—53 specific pathogen-free black domestic shorthair cats. Procedure—Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for ≤ 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats. Results—After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were con...